I did a bit more sleuthing and NOW I'm leaning toward this being a ROKU problem.
I have 2 Roku Ultra's (model 4800X, Software version 10.0.0, build 4209-C2; one connected to a Samsung LED TV and the other to an LG LED TV) and I have an older Roku Streaming Stick (model 3810RW, Software version 10.0.0, build 4209-50; connected to a Toshiba LED TV). All 3 have Paramount Plus version 5.6, build 202107304 loaded.
The color problem that I'm seeing on The Good Fight occurs ONLY on the Ultras. The 3810 Streaming Stick does NOT show the problem (the color is as expected whereas on the Ultras the blue color plain is missing causing the screen to have a distinct pink cast).
The question then is: what did Roku change between the 4209-50 and 4209-C2 builds? It would appear to me that they broke something or changed something in the hardware interface that messes up the way the Roku handles/display color plain data.